How do I clean up the Software Update cache?

[Barry Premeaux]

I had a couple *.iso disks in my CD/DVD drive recently.  I had looked
at the images, but did not install.  Now, i have a software update
prompt and when I go to install, I am asked to put the two iso's in
the drive.  If I cancel the request and try to continue with the
updates, it fails to complete them.  My google efforts have failed to
produce a solution to the problem.  How do I clean this up so that I
can get back to regular updates?  I am running ubuntu 13.04.